1,329 research outputs found
A logarithmic-depth quantum carry-lookahead adder
We present an efficient addition circuit, borrowing techniques from the
classical carry-lookahead arithmetic circuit. Our quantum carry-lookahead
(QCLA) adder accepts two n-bit numbers and adds them in O(log n) depth using
O(n) ancillary qubits. We present both in-place and out-of-place versions, as
well as versions that add modulo 2^n and modulo 2^n - 1.
Previously, the linear-depth ripple-carry addition circuit has been the
method of choice. Our work reduces the cost of addition dramatically with only
a slight increase in the number of required qubits. The QCLA adder can be used
within current modular multiplication circuits to reduce substantially the
run-time of Shor's algorithm.Comment: 21 pages, 4 color figure
Layered architecture for quantum computing
We develop a layered quantum computer architecture, which is a systematic
framework for tackling the individual challenges of developing a quantum
computer while constructing a cohesive device design. We discuss many of the
prominent techniques for implementing circuit-model quantum computing and
introduce several new methods, with an emphasis on employing surface code
quantum error correction. In doing so, we propose a new quantum computer
architecture based on optical control of quantum dots. The timescales of
physical hardware operations and logical, error-corrected quantum gates differ
by several orders of magnitude. By dividing functionality into layers, we can
design and analyze subsystems independently, demonstrating the value of our
layered architectural approach. Using this concrete hardware platform, we
provide resource analysis for executing fault-tolerant quantum algorithms for
integer factoring and quantum simulation, finding that the quantum dot
architecture we study could solve such problems on the timescale of days.Comment: 27 pages, 20 figure
Light Sneutrino Dark Matter at the LHC
In supersymmetric (SUSY) models with Dirac neutrino masses, a weak-scale
trilinear A-term that is not proportional to the small neutrino Yukawa
couplings can induce a sizable mixing between left and right-handed sneutrinos.
The lighter sneutrino mass eigenstate can hence become the lightest SUSY
particle (LSP) and a viable dark matter candidate. In particular, it can be an
excellent candidate for light dark matter with mass below ~10 GeV. Such a light
mixed sneutrino LSP has a dramatic effect on SUSY signatures at the LHC, as
charginos decay dominantly into the light sneutrino plus a charged lepton, and
neutralinos decay invisibly to a neutrino plus a sneutrino. We perform a
detailed study of the LHC potential to resolve the light sneutrino dark matter
scenario by means of three representative benchmark points with different
gluino and squark mass hierarchies. We study in particular the determination of
the LSP (sneutrino) mass from cascade decays involving charginos, using the mT2
variable. Moreover, we address measurements of additional invisible sparticles,
in our case the lightest neutralino, and the question of discrimination against
the MSSM.Comment: 25 pages, 16 figure
Neuromorphic liquid marbles with aqueous carbon nanotube cores
Neuromorphic computing devices attempt to emulate features of biological nervous systems through mimicking the properties of synapses, towards implementing the emergent properties of their counterparts, such as learning. Inspired by recent advances in the utilisation of liquid marbles (microlitre quantities of fluid coated in hydrophobic powder) for the creation of unconventional computing devices, we describe the development of liquid marbles with neuromorphic properties through the use of copper coatings and l.0mgml-1 carbon nanotube-containing fluid cores. Experimentation was performed through sandwiching the marbles between two cup-style electrodes and stimulating them with repeated DC pulses at 3.0 V. Our results demonstrate that 'entrainment∗ of a carbon nanotube filled-copper liquid marble via periodic pulses can cause their electrical resistance to rapidly switch between high to low resistance profiles, upon inverting the polarity of stimulation: The reduction in resistance between high and low profiles was approximately 88% after two rounds of entrainment. This effect was found to be reversible through reversion to the original stimulus polarity and was strengthened by repeated experimentation, as evidenced by a mean reduction in time to switching onset of 43%. These effects were not replicated in nanotube solutions not bound inside liquid marbles. Our electrical characterisation also reveals that nanotube-filled liquid marbles exhibit pinched loop hysteresis IV profiles consistent with the description of memristors. We conclude by discussing the applications of this technology to the development of unconventional computing devices and the study of emergent characteristics in biological neural tissue
Moments of Nucleon's Parton Distribution for the Sea and Valence Quarks from Lattice QCD
We extend the study of lowest moments, , of the parton
distribution function of the nucleon to include those of the sea quarks; this
entails a disconnected insertion calculation in lattice QCD. This is carried
out on a quenched lattice with Wilson fermion. The quark loops
are calculated with noise vectors and unbiased subtractions, and multiple
nucleon sources are employed to reduce the statistical errors. We obtain
5 signals for for the $u,d,$ and $s$ quarks, but is
consistent with zero within errors. We provide results for both the connected
and disconnected insertions. The perturbatively renormalized for the
strange quark at $\mu = 2$ GeV is $_{s+\bar{s}} = 0.027 \pm 0.006$ which is
consistent with the experimental result. The ratio of for vs.
in the disconnected insertion with quark loops is calculated to be . This is about twice as large as the phenomenologically fitted
from
experiments where and include both the connected and
disconnected insertion parts. We discuss the source and implication of this
difference.Comment: 50 Pages 58 Figure
Who pays and who benefits? How different models of shared responsibilities between formal and informal carers influence projections of costs of dementia management
<p>Abstract</p> <p>Background</p> <p>The few studies that have attempted to estimate the future cost of caring for people with dementia in Australia are typically based on total prevalence and the cost per patient over the average duration of illness. However, costs associated with dementia care also vary according to the length of the disease, severity of symptoms and type of care provided. This study aimed to determine more accurately the future costs of dementia management by taking these factors into consideration.</p> <p>Methods</p> <p>The current study estimated the prevalence of dementia in Australia (2010-2040). Data from a variety of sources was recalculated to distribute this prevalence according to the location (home/institution), care requirements (informal/formal), and dementia severity. The cost of care was attributed to redistributed prevalences and used in prediction of future costs of dementia.</p> <p>Results</p> <p>Our computer modeling indicates that the ratio between the prevalence of people with mild/moderate/severe dementia will change over the three decades from 2010 to 2040 from 50/30/20 to 44/32/24.</p> <p>Taking into account the severity of symptoms, location of care and cost of care per hour, the current study estimates that the informal cost of care in 2010 is AU5.0 billion per annum. By 2040 informal care is estimated to cost AUAU16.7 billion per annum. Interventions to slow disease progression will result in relative savings of 5% (AU4 billion) of the cost per annum.</p> <p>With no intervention, the projected combined annual cost of formal and informal care for a person with dementia in 2040 will be around AU35,000.</p> <p>Conclusions</p> <p>These findings highlight the need to account for more than total prevalence when estimating the costs of dementia care. While the absolute values of cost of care estimates are subject to the validity and reliability of currently available data, dynamic systems modeling allows for future trends to be estimated.</p
- …